How many of the following molecules are with non-zero net dipole moment, NH 3   , HCl ,   H 2 O…

Among the given molecules ${\mathrm{BeF}}_2, {\mathrm{CCl}}_4$ and ${\mathrm{BH}}_3$ has zero dipole moment. ${\mathrm{BeF}}_2$ has linear structure and ${\mathrm{BH}}_3$ has symmetrical trigonal planar structure and ${\mathrm{CCl}}_4$ also has symmetrical tetrahedral structure.  

${\mathrm{NH}}_3 ,\mathrm{HCl}, {\mathrm{H}}_2\mathrm{O}$ have non-symmetrical structure.

Hence, their net dipole moment is not zero